In recent years, exercisers are increasing in number with use of the training device in a fitness gym or the like with a health-oriented trend. As a governmental policy, from a viewpoint of care prevention of aged person in order not to be a man requiring caregivers or the like, aged person are increasing in number doing the muscular workout for maintenance in healthy condition or prevention of reduction in physical strength. As such a training device, there are, for example, a leg press machine for strengthening leg muscles or a chest press machine for strengthening chest and arm muscles. As a training device for such a use, a plate weight method applying load to an exerciser with use of a plate weight is principally available. It is, however, hard to perform a fine control of load by this plate weight method. Then, it is hard to do an appropriate muscular workout for each exerciser. Therefore, the training device driven by motor applying load to an exerciser by a torque of the electric motor in recent years is gradually spreading. The training device driven by motor can perform a fine control of load by controlling a torque of the electric motor. As a result, an exerciser can do the muscular workout safely, happily, and effectively.
As the training device driven by motor, for example, the training device being variable in load has been disclosed by detecting a relative movement position of a plate positioned at a tip of leg of leg press machine. In this technology, load of the electric motor is controlled by a load characteristic to be a predetermined position as pre-programmed by detecting a relative movement position between the exerciser and a press board at the time of leg press in the training device. This enables it to make the largest initial load at an initial condition of the leg press, and to make the smallest final load at a final condition thereof together with a relative movement of the press board. Then, the exerciser can do an appropriate muscular workout.
The training device being variable in load has been also disclosed by detecting a relative movement velocity of the press board of leg press machine (for example, Japanese patent unexamined laid-open publication No. 204850 of 2001). In this technology, load of the electric motor is variably controlled in accordance with a change of the relative movement velocity by detecting a relative movement velocity of the press board at the time of leg press in the training device. Then, load can be gradually reduced in case where a relative movement of the press board becomes slow at the time of leg press. As a result, load can be reduced according to a degree of fatigue of the exerciser. Then, the promotion of continuation of the muscular workout and an achievement of target momentum to the exerciser can be obtained.
A muscle can be exerted only in a direction to be contracted. However, there are two kinds of exercises, that is, a concentric exercise and an eccentric exercise as the muscular workout. The concentric exercise is an exercise, exerting a force while the muscle contracts. For example, the leg press movement is an exercise stretching a knee while the press board is pressed. For example, the leg press exercise is an exercise doing in a direction bending the knee while the press board is pressed. Then, the muscle is exerted a force in a direction to be contracted while a quadriceps is stretched. The eccentric exercise is an exercise exerting a force while the muscle is stretched. For example, the leg press exercise is an exercise exerting a force in a direction bending the knee while the press board is pushed. Then, the muscle is exerted a force in a direction to be contracted while the quadriceps are stretched.
In general, it is said that the eccentric exercise is more effective in strength of muscle than the concentric exercise. The reason is that the eccentric exercise is larger in damage of muscle fiber caused by exercises than the concentric exercise. A muscular hypertrophy of the eccentric exercise can be easily obtained by damage repair process, compared with the concentric exercise.
However, the eccentric exercise is an exercise having a high frequency of tardive muscle pains. It is said that the concentric exercise is appropriate for aged person, patients doing rehabilitation, or injured person rather than a professional athlete. The concentric exercise is more preferable than the eccentric exercise as training for maintenance in healthy condition and prevention of reduction in physical strength. For example, in case of a training done by a device such as conventional leg press machine, it is designed to push the press board in case of stretching a knee (doing a leg press exercise) and to pull the press board in case of bending a knee (an exercise applying force in a reverse direction with such a leg press exercise is referred to as a full concentric exercise in this specification). Accordingly, it is preferable that either case of reciprocal motion of a tip of leg falls into the concentric exercise (doing the concentric exercise in both of the reciprocating and bidirectional directions is referred to as a full concentric exercise). In this case, it falls into a concentric exercise done by hamstrings in case of bending a knee. In addition, the full concentric exercise cannot be obtained in the training device of plate weight method. However, the full concentric exercise can be obtained by changing a direction of load by changing a direction of exercise of the press board in the training device driven by motor.